In the past, from the viewpoint of realizing effective utilization of resources, there is proposed an image forming apparatus that directly reuses, as a print sheet, a sheet that passes through the image forming apparatus. In this related art, it discloses an image forming apparatus that controls processing for reusing a sheet that passes through the image forming apparatus. The image forming apparatus detects, with a sensor, dirty spots on both the sides of a sheet to be reused, which is fed from a paper feeding cassette. When a dirty spot is detected only on one side of the sheet, the image forming apparatus forms, with effective image forming means, an image only on the other side on which a dirty spot is not detected. When no dirty spot is detected on both the sides of the sheet, the image forming apparatus accumulates the sheet in a reverse side paper tray without performing image forming processing. When dirty spots are detected on both the sides of the sheet, the image forming apparatus discards the sheet in a waste tray.
However, in the above related art, since image formation is not performed on the side on which the dirty spot is detected, it is difficult to say that the sheet is sufficiently reused. For example, even when a region including the dirty spot in the sheet and a transfer region in the sheet to which a developer image is transferred do not overlap each other, the sheet is discarded. Therefore, the sheet cannot be effectively utilized. The present invention has been devised to solve the problem and it is an object of the present invention to provide an image forming apparatus that enables effective utilization of a sheet.